There are various languages using prosody. For example, Chinese uses prosody called tones. Tones are sound pitch patterns used to distinguish between meanings, and mainly, vowels have unique tones such as rising and falling tones. It is therefore important to recognize the tones for recognition of Chinese speech.
A technique disclosed in Japanese Patent No. 3162994 (reference 1) is known as a speech recognition technique using tones. The Chinese speech recognition technique described in reference 1 divides a syllable into a first half portion and a second half portion, associates only the second half portion of the syllable with a tone, and recognizes speech using the associated tone. Since speech recognition is executed using tones, this technique can make the voice tone speech recognition accuracy higher than in a technique without using tones.